Agreed, but a lot of sci-fi/fantasy suffers from this. How many times for example did we see in Star Trek the magical engineering solution of the week to solve a plot problem only to be forgotten about as a possible solution to a like problem 3 episodes later?
The difference here is that a machine--engines--are easily subject to breakdowns, repairs no longer working, updates going through paces before functioning properly. Jedi are not machines--their power is as much a part of their makeup as their organs, so the use of this power by trained individuals should not suffer from highs and lows, forgotten skills, etc.
There are so many huge differences between specific Jedi skill they all possess, that it renders the characters as flimsy to support weak writing. One of the most glaring examples is Jedi speed used early in The Phantom Menace
, but when a character would need it most...nothing. All we have are fan excuses of Kenobi being tired after the fall/leap, which was never implied on screen.
Everyone knows Qui-Gon had to be separated in order for Maul to kill him (well, that was what Lucas had us believe)....but the same result could have been accomplished with Kenobi in the mix. Numbers did not stop Sidious from killing Jedi in his office.